Sea urchin (Strongylocentrotus intermedius) polysaccharide enhanced BMP-2 induced osteogenic differentiation and its structural analysis

•A non-sulphate glucomannan (SUP) was isolated from Strongylocentrotus intermedius.•SUP remarkably promoted the BMP-2 activity and induced osteoblast differentiation.•The molecular structure of SUP was elucidated by two-dimensional NMR spectrum.•Sulphate group not essential for polysaccharide enhances osteogenic differentiation. A new sea urchin polysaccharide (SUP) was extracted from the gonad of sea urchin (Strongylocentrotus intermedius), and its bioactivity to synergistically enhance the functionality of bone morphogenetic protein-2 (BMP-2) induced osteoblastic differentiation was characterized. Results showed that the SUP is homogenous with an average molecular weight of 4.4 kDa, and it is mainly composed of mannose with a small number of glucose and N-acetylglucosamine, with a backbone of alternating 1, 4-D-Man and 1, 3-D-Man residues. The SUP was shown to synergistically enhance BMP-2 induced osteoblastic differentiation in C2C12 myoblast cells, evidenced by a significant increase in the activity of alkaline phosphatase (ALP), when the concentration of the SUP was higher than 10 µg/mL. The elevated ALP activity was also confirmed by histochemical staining of C2C12 myoblast cells. These results suggest that the SUP can promote bone regeneration and may serve as a functional food supplement for bone health.